up3

server/block/cube/rotation.go

@@ -0,0 +1,101 @@
+package cube
+
+import (
+	"github.com/go-gl/mathgl/mgl64"
+	"math"
+)
+
+// Rotation describes the rotation of an object in the world in degrees. It
+// holds a yaw (r[0]) and pitch value (r[1]). Yaw is in the range (-180, 180)
+// while pitch is in the range (-90, 90). A positive pitch implies an entity is
+// looking downwards, while a negative pitch implies it is looking upwards.
+type Rotation [2]float64
+
+// Yaw returns the yaw of r (r[0]).
+func (r Rotation) Yaw() float64 {
+	return r[0]
+}
+
+// Pitch returns the pitch of r (r[1]).
+func (r Rotation) Pitch() float64 {
+	return r[1]
+}
+
+// Elem extracts the elements of the Rotation for direct value assignment.
+func (r Rotation) Elem() (yaw, pitch float64) {
+	return r[0], r[1]
+}
+
+// Add adds the values of two Rotations element-wise and returns a new Rotation.
+// If the yaw or pitch would otherwise exceed their respective range as
+// described, they are 'overflown' to the other end of the allowed range.
+func (r Rotation) Add(r2 Rotation) Rotation {
+	return Rotation{r[0] + r2[0], r[1] + r2[1]}.fix()
+}
+
+// Opposite returns the Rotation opposite r, so that
+// r.Vec3().Add(r.Opposite().Vec3()).Len() is equal to 0.
+func (r Rotation) Opposite() Rotation {
+	fixed := r.fix()
+	return Rotation{fixed[0] + 180, -fixed[1]}.fix()
+}
+
+// Neg returns the negation of the Rotation. It is equivalent to creating a new
+// Rotation{-r[0], -r[1]}.
+func (r Rotation) Neg() Rotation {
+	fixed := r.fix()
+	return Rotation{-fixed[0], -fixed[1]}
+}
+
+// Direction returns the horizontal Direction that r points towards based on the
+// yaw of r.
+func (r Rotation) Direction() Direction {
+	yaw := r.fix().Yaw()
+	switch {
+	case yaw > 45 && yaw <= 135:
+		return West
+	case yaw > -45 && yaw <= 45:
+		return South
+	case yaw > -135 && yaw <= -45:
+		return East
+	case yaw <= -135 || yaw > 135:
+		return North
+	}
+	return 0
+}
+
+// Orientation returns an Orientation value that most closely matches the yaw
+// of r.
+func (r Rotation) Orientation() Orientation {
+	const step = 360 / 16.0
+
+	yaw := r.fix().Yaw()
+	if yaw < -step/2 {
+		yaw += 360
+	}
+	return Orientation(math.Round(yaw / step))
+}
+
+// Vec3 returns the direction vector of r. The length of the mgl64.Vec3 returned
+// is always 1.
+func (r Rotation) Vec3() mgl64.Vec3 {
+	yaw, pitch := r.fix().Elem()
+	yawRad, pitchRad := mgl64.DegToRad(yaw), mgl64.DegToRad(pitch)
+
+	m := math.Cos(pitchRad)
+	return mgl64.Vec3{
+		-m * math.Sin(yawRad),
+		-math.Sin(pitchRad),
+		m * math.Cos(yawRad),
+	}
+}
+
+// fix 'overflows' the Rotation's values to make sure they are within the range
+// as described above.
+func (r Rotation) fix() Rotation {
+	signYaw, signPitch := math.Copysign(180, r[0]), math.Copysign(90, r[1])
+	return Rotation{
+		math.Mod(r[0]+signYaw, 360) - signYaw,
+		math.Mod(r[1]+signPitch, 180) - signPitch,
+	}
+}